This disclosure is related to a process for purification of a vent stream. In particular, this disclosure is related a process for removing halogenated compounds from polyolefin vent streams generated during the manufacturing of a polymer.
Catalysts are often used in the manufacturing of polymers especially polyolefins. Minor amounts of the catalyst used in the manufacture of polyolefins form multi-fluorinated by-products (e.g., pentafluoro-benzene (PFB) and other fluorinated benzene molecules) and other halogenated by-products (hereinafter collectively termed halogenated by-products) in small quantities. The by-products are contained in the vent stream that is discharged from the polyolefin manufacturing facility to control the rate of build-up of these products in the manufacturing process. These vent streams are most often sent to an adjacent hydrocarbon facility in order to collect and reprocess the valuable ethylene contained in the stream.
Even in small quantities, the presence of these halogenated by-products in the vent stream dictates that the vent streams are transported to the heavier hydrocarbon processing side of the process, where some of the halogenated materials are converted to hydrogen fluoride, which is highly corrosive. If these trace amounts of hydrogen fluoride are not removed from the vent stream, severe corrosion of the manufacturing facility can occur. The alternative is to incinerate (destroy) the vent stream and with it the valuable ethylene stream that can be salvaged.
It is therefore desirable to capture some of the halogenated by-products that are present in the vent stream thus reducing the level of halogenated species to an acceptable level while at the same time recovering ethylene contained in the stream and using it to manufacture additional polymer.